EMERGENCE OF QUANTUM (WAVE) CHAOS IN CYLINDRICAL CAVITIES WITH A SINGULAR PERTURBATION
E. M. Ganapolskii
Frequency spectra of quasioptical cylindrical microwave resonator with housed thin metal rods, which act as singular perturbations, are experimentally studied in the frequency range 26…38 GHz. The dependence of the spectrum character on the number of rods perturbations is determined. It is found that the Poisson distribution of inter-frequency intervals is observed when there are a small number of perturbations in the spectrum. This indicates that in this case the system is quasiregular and there are signs of quantum chaos (QC) in it. However, when the number of singularity increases, the system spectrum changes qualitatively: the distribution of inter-frequency intervals is close to the Wagner distribution, which indicates the appearance of levels “repulsion” in the spectrum and the presence of QC in the systems. Thus, it is experimentally established that QC occurs in quasiregular system only when there is a sufficiently large number of singular perturbations.
A NUMERICAL ANALYTICAL METHOD FOR SOLVING PROBLEMS OF ELECTROMAGNETIC WAVE DIFFRACTION BY NON-UNIFORM ANISOTROPIC LAYERS
A. V. Brovenko, P. N. Melezhik, A. Y. Poyedinchuk
A numerical analytical method is proposed for finding reflection and transmission amplitudes of a plane linearly polarized electromagnetic wave obliquely incident on a non-uniform anisotropic dielectric layer, the tensor elements of which depend on a single spatial coordinate. The method is based on constructing a special case solution to the Riccati equation for the Cauchy problem and enables a qualitative description of the wave diffraction by the electrodynamical structure of the type within a unitary framework. The method efficiency is demonstrated by the numerical solution results obtained for a set of diffraction problems on non-uniform gyrotropic plasma-like layers. Long-wave asymptotics of the reflection coefficient of a plane homogeneous wave have been obtained in the case of its incidence on a non-uniform gyrotropic layer whose tensor elements do not depend on the frequency parameter.
THE COMPARATIVE ANALYSIS OF MODELS FOR ESTIMATION OF THE TOTAL MOISTURE CONTENT OF THE TROPOSPHERE THROUGH THE GPS MEASUREMENTS OVER KHARKOV
A. L. Kovorotniy, Y. V. Goncharenko, V. N. Gorobets, F. V. Kivva, A. I. Gorb, A. Y. Balan
The humidity and its space-time distribution is one of the meteorological parameters having impact on the micro wave propagation in the atmosphere. The results of measurements of the moisture content of troposphere by navigation satellite system of GPS over the Kharkov region are presented in the paper. Those results are evaluated on the basis of precipitated water values in vertical column above the receiver obtained by different models. The comparison of the results of 10 different tropospheric models at different weather conditions is provided in the paper. Two models have certain advantages – Saastamoinen for summer and Hophield for spring and autumn periods, which reflect some regional characteristics of the troposphere associated with the characteristics of air circulation and temperature control. Using the optimal model for the PWV prediction allows to decrease the estimation error of the total water content determination in 3…5 times.
DISAMBIGUATION FOR SOLVING THE INVERSE PROBLEM OF RECONSTRUCTION OF RAIN INTENSITY USING DOUBLE-FREQUENCY RADAR SOUNDING
G. Khlopov, G. Veselovska, O. Voitovych
We analyzed the radar cross section dependence of raindrops on their diameter for different wavelengths by using numerical simulation. It is shown that in the short microwave range (λ< 3.2 cm), the dependence has nonmonotonic character due to resonant scattering of electromagnetic waves by raindrops. Using combination of operating wavelengths λ1 = 3.2 cm, λ2 = 10 cm, and λ1 = 5.5 cm, λ2 = 10 cm does not allow to use a double-frequency method of remote sensing for recovery of microstructural parameters of precipitation, because the dependence of the differential radar cross section on size of particle is practically absent. We obtained the system of inequalities, which allows to solve the problem of ambiguity when recovering rain intensity according to the double-frequency sensing by using shorter wavelength λ1 = 8 mm. It is shown that the use of the long-wavelength range of microwave band leads to decrease of the radar reflectivity value for small raindrops and it requires a significant increasing of energy potential of weather radar and tightens the requirements for the accuracy of the measurement.
MEASURING PLACES ANGLES OVER THE SEA USING ROOT-MUSIC METHOD. CHOICE OF SOLUTIONS
Y. A. Pedenko
This paper presents results on the problem of increasing the accuracy of radar elevation angle measurements of the low-altitude targets above the sea using the root-MUSIC algorithm, which is considered by experts as a one of the means of addressing this problem. One of the tasks, without which it can not be an effective use of this algorithm, is virtually unexplored task of choosing a solution that meets the target, from an aggregate of several solutions the number of which is defined by the dimension of the signal subspace. In this paper, the distribution of the aggregate of measured elevation angles are obtained and analyzed by computer simulations for different degrees of the sea state, with varying number of spatial samples at a given aperture of the antenna array and the dimension of signal subspace. Standard errors of measurement elevation angle as a function on target elevation angle are calculated using different rules of choice the solution. The requirements for the antenna arrays used in the elevation angle measuring devices were developed. The rules which effectively solve the problem of the correct choice were proposed. The results of the study extend the knowledge of how to improve the methods and devices destined for measuring the target elevation angle above the sea.
A. P. Nickolaenko
The long-term observations of the seasonal variations of the first Schumann resonance frequency observed in the vertical electric field component are compared with the changes of median solar time (analemma). The records of the Hungarian observatory Nagycenk (47.6° N, 16.7° E) are used. Daily variation of the peak frequency were averaged for each month and thus the diurnal range was determined. We use both the seasonal variations of this range and the sum of its annual and semi-annual components found by means of singular spectrum analysis (SSA). It is demonstrated that the diurnal-seasonal changes are reproduced year after year. A comparison was made between the global electromagnetic resonance data and the periodic changes of the mean solar time. The latter are caused by the ellipticity of the Earth's orbit, which results in displacement of the visible center of the solar disk. It outlines the looped curve in the sky during the year (analemma). For the first time correlation analysis of the continuous ten-years-long records is performed and an outstanding similarity of electromagnetic and astronomical data is demonstrated. An explanation is suggested for the link of the two seemingly dissimilar processes.
ANALYSIS OF THREE DIFFERENTIAL GPR SYSTEMS FOR SUBSURFACE IMAGING
L. A. Varianytsia-Roshchupkina, G. Gennarelli, F. Soldovieri, G. P. Pochanin
Quality of the radar images of the detected objects directly depends on the quality of the obtained GPR data. One of the ways to increase the information content of such data is to use not traditional (monostatic, bistatic) but alternative (e. g., differential) antenna systems. The goal of this work is to analyze and compare possibilities of imaging using differential antenna systems with receiving antennas displaced symmetrically with respect to the transmitting antenna along three orthogonal directions. To this end, synthetic radargrams are generated by the finite-difference time-domain forward solver for each measurement setup. After that a microwave tomographic approach is applied to process the scattered field differential data and to facilitate the comparison among these systems. As a result, it was obtained that the system with antennas displaced along the vertical axis is the only one capable to provide a reliable image regardless of the shape of the object. The performed studies have shown the prospects of such system application in the practical GPR problems.
V. A. Kabanov, G. M. Morgun, V. B. Sinitsky, I. S. Tourgenev
The operational assessment of a troposphere refraction is the actual task which is necessary for increasig the efficiency of radio engineering systems. The results of experimental investigation of a troposphere refraction over the sea using the signals of GPS navigation system satellites are presented. The feature of work is the using of a shadow zone in which characteristics of signals are most changeable and sensitive to refraction variations. The parabolic antenna is applied to amplify GPS signals in the shadow zone. In the experiments using radio setting of GPS satellites over the sea, the patterns of the signals are observed corresponding to standard, heightened refraction and the waveguide propagation. The gradients of a high-rise profile of refraction coefficient of a troposphere surface layer are restored from experimental data. They are calculated according to the developed model, on an angle of radiosetting and on the slope of a diffraction site of an attenuation factor. The gradients restored from satellites data are compared to the effective gradients restored from signals levels on the near-water over-the-horizon path. Correlation coefficients of the gradients determined by data on the near-water and satellite paths, on counting in close sessions make ~0.53…0.78, when averaging data increase approximately to 0.85…0.9. The results of the carried out experiments can be used for development of satellite troposphere refraction diagnostics systems.
A .V. Dormidontov, Y. V. Prokopenko, S. I. Khankina, V. M. Yakovenko
One of the urgent problems of modern radiophysics is the study of the fundamental properties of solid-state structures that contain nanodimension fragments. Studies of the excitation mechanisms of electromagnetic waves when the charged particles move in various electrodynamic systems form the basis of electronics. In this case, a number of the fundamentally important characteristics of structures includes their dispersion equations. They allow to determine the place of electrodynamic structures in the radio physical systems of different purposes. An energy loss of a charged particle per unit time on the waves and/or oscillations excitation in the system is the data characteristic. Dispersion equations characterizing the eigenmodes of semiconductor (or dielectric) cylinder with layer of 2D electron gas on a side surface thereof were obtained in electrostatic approximation, and the energy loss of charged particle were determined when it was moving along a spiral path around such a structure. The dispersion dependences of eigen slow waves of system were obtained, and the energy loss of a particle moving in an external magnetic field with the electric-field vector that directed parallel to the longitudinal axis of cylindrical structure symmetry were found. The features of the gyrosynchrotron resonance of system (of Doppler effect) were determined. The structures of both the plasma layer and without it were studied when their eigenfrequencies are in the terahertz range. A comparison of the spectra of eigenfrequencies of the studied systems was made. The influence of surface plasma layer with nanodimension thickness on the eigenfrequencies of semiconductor and dielectric cylinders was studied. Research results extend our conceptions about the electrodynamic properties of systems with plasma mediums and systematize the knowledge of the excitation mechanisms of electromagnetic waves in electrodynamic systems that form the basis of microwave devices.
V. S. Miroshnichenko, E. A. Kovalev
Obtaining the sufficient interaction length in diffraction radiation oscillators, which are working on THz-frequencies, is the actual problem of diffraction electronics. One of the ways to resolve this problem is the use of composed focused mirror in the open resonant system. The work goal is the experimental investigations of the resonant modes properties in open resonant system with focused mirror, composed of several cylindrical reflectors, having the same radius of curvature. For H-polarization of modes the field distributions and Q-factor on frequencies f = 25÷38 GHz are obtained, when the focused mirror was composed of two, three and four cylindrical reflectors. The use of the focused mirror, composed of 2 reflectors, is more attractive for diffraction radiation oscillator working on TEM00q-resonant mode. When the focused mirror is composed of n ≥ 2 cylindrical reflectors, the best properties are obtained for TEM(n–1)0q-modes, when having the null of resonant field near the attachment of reflectors. So, when n = 2 the field distribution of TEM10q-mode is supergaussian.
V. P. Ruban, O. O. Shuba, O. G. Pochanin, G. P. Pochanin
The use of analog accumulation in a sampling converter increases the dynamic range of the sampling receiver. However, there is no information about the analog accumulation effect on the sampling converter performance in the scientific literature. To clarify it, the authors have solved the model problem of sampling conversion and performed appropriate experiments to verify theoretical conclusions. The influence of analog accumulation on such sampling converter characteristics as the transmission coefficient, the transient response, the operating frequency band has been investigated. The investigation has shown that analog accumulation leads to reducing the rise time of the transient response and, accordingly to broadening the operating bandwidth of the sampling converter. The transmission coefficient remains constant at that. The investigation results are useful for practice in order to create highly sensitive UWB equipment.
M. I. Dzyubenko, V. K. Kiseliov, V. P. Radionov
Measurement of the refractive index of transparent materials in the terahertz (THz) range is required for the development of devices and systems that operate in this range. Submillimeter lasers are one of the most affordable sources of coherent THz radiation. They have features that allow one to measure the refractive index of transparent materials. The method for on-line measuring the refractive index of transparent materials in the terahertz range is represented. The measurable substance is placed in a quasi-optical resonator. Measurements are performed by means of coherent terahertz electromagnetic radiation. The test measurements of the refractive index are performed. We provided justification of reducing the error of the refractive index measurement, taking into account the physics of the processes in the space of resonance submillimeter laser system. It was shown that the accuracy of measurement of the refractive index can be greatly increased by placing the test substance in the resonator THz laser. The presented techniques for measuring the refractive index of transparent materials in the THz range can be used in various fields of science, technology and medicine.